1. Field of the Invention
The present invention relates to method and circuit for drive control of electronic timepiece with generator, charger or chargeable battery.
2. Background Art
There are electronic timepieces having generators and timepiece circuits driven by the power supplied from the generators. There are other types of electronic time pieces having timepiece circuits, chargeable power sources such as chargeable battery or capacitor in them or as a removable unit for storage of electricity, and in the chargeable power source store electrical power supplied from internal or external generators, and operate by the power. As generators for electronic timepieces, there are some ways such as a rotating-type generator driven by kinetic energy which is seized by an oscillating weight and the like, and such as solar cell and the like which seizes light energy. For chargeable batteries for electronic timepieces, some of them receive electrical energy generated by external generators with electrically direct connection or induction by electromagnetic wave.
There are some requests to the stated electronic timepiece having generating function or electricity storing function. One is to make it possible to keep stability of initial time displaying operation after left untouched for a long time. Another one is to regain regular circuit operation when the stored electrical power decreases and the circuit operation stops and then the stored electricity returns. Another one is to inform a user of precise remaining stored electricity. Prior arts trying to meet these demands are disclosed in International Publication WO98/06013 entitled xe2x80x9cElectrical timepiecexe2x80x9d, Japanese Patent Application Laid-Open Publication No. 11-64546 entitled xe2x80x9cAn electronic apparatus with generating apparatus and resetting method of an electronic apparatus with generating apparatusxe2x80x9d, and Japanese Patent Application Laid-Open Publication No. 11-64548 entitled xe2x80x9cAn electronic apparatus with generating apparatus, a controlling method over a power source state of an electronic apparatus with generating apparatus, and a storage media storing a program which controls a power source state of an electronic apparatus with generating apparatusxe2x80x9d. Next, the outlines and technical limits of these prior arts written in the above publication will be described.
International Publication WO98/060presents two following techniques. The first is a technique by which, when the stored electricity decreases below a prescribed reference voltage, a time display is stopped, and when a condition for returning operation is satisfied, time keeping operation is resumed and continued at least, for a prescribed period. The second is a technique by which when the stored electricity decreases below a prescribed reference voltage, a time display is stopped, and when a generation detect means detects generation of electrical energy more than a prefixed level, time keeping operation is resumed and continued at least for a prescribed period. In the first technique, when a detection of time-setting is performed by user, the condition for returning operation is satisfied. Therefore time keeping operation can be resumed even when charging to the storing means is not occurring. Under this condition, without charging to the storing means, time keeping operation can be resumed and stopped again and again, the stored electricity is consumed. Therefore the stored electricity is easily to stray off the prescribed condition to continue to keep time, and it becomes impossible to guarantee a notified time for time-keeping.
At the same time, in the first technique, when detection of a meeting the condition for operation return is made, time keeping operation is resumed, and the above reference voltage is lowered by one level, thereby the resumed time keeping operation will be continued until the stored electricity decreases less than the changed reference voltage. In this case, the stored electricity required for resuming; time keeping operation after stopping declines step by step. Therefore, when this action is carried out several times, time keeping operation will be executed even until the stored electricity is low. Then there is a possibility that after the timepiece drive circuit is stopped, a leakage current in the timepiece drive circuit consumes the stored electricity to almost null in a short time. When the timepiece is again used, the stored electricity requires long charging time to reach a drive starting potential for the timepiece, resulting in worsen resuming response, which is a problem in this technique.
On the other hand, in the second technique, when the generation detect means detects more electrical energy generated than a prefixed threshold level, time keeping operation is resumed. Therefore, under some relation between stored electricity and the threshold level, there is a possibility that even a generation which does not charge can resume the timepiece. In this case, resuming and stopping of the timepiece are alternatively repeated without charging. This results in consuming the stored electricity. As a result, the prescribed condition to continue to operate the timepiece is missed more quickly, therefore there is a possibility of failing to guarantee a notified timepiece operation period.
Japanese Patent Application Laid-Open Publication No. 11-64546 presents a technique, in which, after a battery voltage falls below a drive voltage for timepiece and operation of circuits of the timepiece is stopped, if charging is resumed by the soler cell and then battery voltage returns larger than the drive voltage for timepiece, a reset signal will be emitted to return the operation of the circuits to normal operation. In this technique, however, the circuit operation will be conducted until the battery voltage becomes below the drive voltage for timepiece. There is a possibility that, after the battery voltage declines below the drive voltage for timepiece and circuits is stopped, if the timepiece is left, untouched, a leakage current in the circuits consumes the stored electricity to almost, null in a short time. Then when the timepiece is again used, the stored electricity requires long charging time to reach a drive starting potential for the timepiece, resulting in worsen resuming response, which is a problem in this technique.
Furthermore, when the battery voltage becomes larger than the drive voltage of the timepiece, a reset signal is emitted and circuits are resumed. Therefore, without generation by solar panel and the like, a self return characteristic of batteries can possibly resume the timepiece or the circuit. In this case, because the stored electricity in the battery is small, the operation does not continue long. The repetition of this operation consumes the stored electricity in the battery to almost null in a short time. Therefore, when the timepiece is again used, the stored electricity requires long charging time to reach a drive starting potential for the timepiece, resulting in worsen resuming response, which is a problem in this technique.
Japanese Patent Application Laid-Open Publication No. 11-64546 presents a technique that a user is notified of a consumption condition of the battery, this resulting in a preventive attempt for the timepiece from stopping suddenly without notification. The way to achieve the purpose is to display an indication for battery remaining amount when the battery voltage falls and the voltage detection result becomes below a first voltage, to prohibit an operation of a buzzer or an electroluminescence element for illuminating the display section when the voltage detection result falls below a second voltage, and to prohibit the time display operation when the voltage detection result falls below a third voltage. This techniques makes a notification, based on the voltage detection results, of the consumption condition of the battery by the above operation of the timepiece. However, relation between battery voltage and stored electricity differs based on charging condition, unevenness of battery quality, quality deterioration, temperature characteristic, and the like. Therefore, even the identical voltage does not mean the same possible operation time, and resulting in the possibility that precise notification of the consumption condition of the battery is not attained. Especially at the last discharging stage of the battery, that is in the time just before the timepiece stops, it is desirable to notify a user of more precise remaining time of the timepiece operation. However, under this technique, there is a possibility that, under a certain condition, the timepiece stops before the user confirms it.
By taking the above situation into considering, the object of the present, invention is to provide an electronic timepiece and its electronic circuit with a drive control method which can attain stabler time keeping operation when the stored electricity is small, quicker response when resuming, and more precise notification of remaining time of the operation.
In order to solve all the above problems, the present invention provides an electronic timepiece comprising a battery capable of charging, a charging section for charging the battery, a timepiece drive circuit operating time keeping operation by using a stored electric power in the battery, a displaying section for displaying time kept by the timepiece drive circuit, a voltage detecting section for detecting a stored voltage, of the battery, a charging detecting section for detecting a state of charging by the charging section, a control section for executing a forcible stop upon an operation of the timepiece drive circuit to reduce or stop a consumption power of the timepiece drive circuit when satisfying, for a prescribed time, a first condition that the stored voltage detected by the voltage detecting section is lower than a first prescribed voltage which is higher than an operation stop voltage of the timepiece drive circuit, and a second condition that a detection result of the charging detecting section indicates that the battery is not charged, and for lifting the forcible stop upon the time keeping operation when the detection result of the voltage detecting section or the charging detecting section satisfies a prescribed operation return condition.
Under the above construction, in a case in which the battery voltage declines and becomes lower than a first pre-scribed voltage which is higher than the timepiece drive circuit stop voltage, when the charging detect function measures non-charging state for a pre-scribed time period, a forcible stop is done upon the time keeping operation by lowering or shutting off a current for the timepiece drive circuit. By this, at the first voltage that is higher than the timepiece drive circuit stop voltage, the forcible stop is done upon the time keeping operation, and at the same time, operation current is lowered or shut down, hence it takes longer for battery voltage to decline to a degree of around zero volt, and it becomes possible for the timepiece to resume in a short charging time period when used next time. After the battery voltage falling below the first pre-scribed voltage, when non-charging state lasts for a pre-scribed time period, timepiece operation will stop. Hence it is possible to guarantee users precise remaining time of the time keeping.